Synopsis: Superfluid Shielding

Separated Bose-Einstein condensates can be shielded from external forces if immersed in a superfluid bath.
Synopsis figure
William Cody Burton/MIT

Put an object with the same density as water in a bath, and it will become neutrally buoyant—it neither sinks nor rises. The upward force of the water on the object will counteract the gravitational force. Wolfgang Ketterle from the Massachusetts Institute of Technology, Cambridge, and colleagues have now shown that clouds of chilled atoms known as Bose-Einstein condensates (BECs) can, in some sense, be neutrally buoyant too. They found that immersing separated BECs in a superfluid bath, itself a BEC, shields them from disturbances such as external forces.

The researchers started with a BEC containing two components—each with all atoms in one of two spin states—in a common superfluid state. They then loaded this BEC into an optical lattice and applied a magnetic-field gradient to the system. This tilted the lattice and split one of the components into several BECs. In this setting, the quantum phases of the separated BECs evolve in a manner determined by the applied magnetic force, causing their interference pattern to undergo so-called Bloch oscillations. By contrast, the other component, which didn’t feel the tilt, remains a connected superfluid and acts as a bath.

By monitoring the Bloch oscillations, the authors demonstrated that the superfluid bath greatly extends the relative phase coherence of the separated BECs. It turns out that the bath shields the separated BECs from external forces and from fluctuations in their self-interaction energy that would otherwise get them out of phase. This shielding occurs because the superfluid is free to change its density distribution in a way that cancels out these disturbances. The findings are particularly relevant for atom interferometry experiments, which rely on the phase coherence between quantum systems to produce precise results.

This research is published in Physical Review Letters.

–Ana Lopes

Ana Lopes is a Senior Editor of Physics.


More Features »


More Announcements »

Subject Areas

Atomic and Molecular Physics

Previous Synopsis

Atomic and Molecular Physics

Hydrogen Clusters Go Negative

Read More »

Next Synopsis

Related Articles

Synopsis: Quantum Sensing of Magnetic Fields
Quantum Physics

Synopsis: Quantum Sensing of Magnetic Fields

A new design for an atomic magnetometer utilizes so-called quantum nondemolition measurements to detect very weak magnetic-field signals. Read More »

Focus: New View of Cold Atoms Flowing
Atomic and Molecular Physics

Focus: New View of Cold Atoms Flowing

A new technique produces an image of the flow of cold atoms through a channel, a potentially important tool for future cold-atom technology. Read More »

Viewpoint: Seeing Scrambled Spins
Atomic and Molecular Physics

Viewpoint: Seeing Scrambled Spins

Two experimental groups have taken a step towards observing the “scrambling” of information that occurs as a many-body quantum system thermalizes.   Read More »

More Articles